This invention relates to a spout for recovery boilers, such boilers being used in the papermaking industry.
During normal recovery boiler operation, the lower part of the boiler furnace is filled with hot, molten liquid. This liquid continually empties from the recovery boiler by means of a spout. Typically, a spout will last about two weeks due, it is believed, to degradation of the spout by the high temperture of the molten liquid. Replacement of the spout not only entails the cost of a spout, but shut-down time of the recovery boiler because the boiler cannot operate while the spout is being replaced.
In order to lessen the deleterious effects of high temperature caused by contact with the molten liquid, such spouts have been water cooled. This is effected by providing the spout with an internal cavity, wherein a coolant liquid, such as water, is fed into the hollow spout and is then led away from the interior of the spout for cooling and subsequent recirculation. U.S. Pat. No. 1,625,755 issued to Williams shows a water cooled smelter spout formed of two semi-cylindrical sections and joined together in such a manner as to define a coolant cavity between them. The cavity is in fluid communication with an inlet pipe or tube and an outlet tube.
Another prior art water cooled boiler spout has been marketed by Babcox and Wilcox Company and includes a spout having a main or forward internal cavity and also having a rear cavity, the rear cavity defined by a housing portion adapted to mount on the lower furnace of the recovery boiler. This spout is mounted in such a way that the molten smelt exiting the recovery boiler flows through the spout trough. This has been used prior to this invention but has exhibited the drawback of breaking down approximately every two weeks, such breakdown believed to be due to thermal metal fatigue caused by concentration of heat at one or more portions of the spout.